Hydrocarbons are produced by drilling into subterranean hydrocarbon-bearing formations. Producing unconsolidated formation walls can result in sand or silt accumulating in the wellbore, which can ultimately cause various problems in the drilling operation. For instance, accumulated sand and rock particles may plug the wellbore formation, resulting in reduced production. Over the years, many methods of preventing sand from entering the wellbore along with the hydrocarbons have been developed, including gravel packing and use of sand screens. Sand control has become increasingly important in the industry.
Gravel packing is a commonly used method to keep formation sand in place and out of the well stream. Gravel packing entails placing a perforated base pipe or a well screen into the wellbore and packing the surrounding annulus with gravel of a desired size. The gravel serves as an additional filter medium to keep sand and fine particulates out of the production stream and provides support to the surrounding formation walls to prevent collapse.
Well screens used in sand control applications can be of various types, including wire mesh and continuous slot wire wrapped. Continuous slot wire wrapped screens are composed of wire helically wrapped around multiple support ribs to form a cylindrical screen with a continuous helical slot. It is important that slot size is maintained within determined tolerances throughout the length of the screen.
Wire wrapped screens are typically manufactured using wire wrapping machines that simultaneously wrap and weld the wire around multiple support ribs to form a hollow cylindrical well screen of a desired length. A spindle rotates the ribs causing wire to be wrapped around the set of ribs.
An important aspect of the manufacturing process is consistent, uniform welds. The present invention provides an improved apparatus and method for maintaining consistent weld pressure during the welding process at faying surfaces of the wrap wire and the ribs.